Drupal Best Practices: Scalability Considerations for High-Performance Sites

As your Drupal website grows in traffic, content, and complexity, it’s crucial to ensure that your infrastructure and architecture are scalable. Scalability allows your site to handle increasing numbers of users, data, and interactions without compromising performance or stability. Building your Drupal site with scalability in mind will help you avoid bottlenecks and ensure smooth, uninterrupted service for your users, even as traffic spikes.

In this blog post, we’ll cover two essential scalability considerations for Drupal sites:

Multisite or Headless Drupal: Decide whether your project requires a multisite setup or if you can use a headless approach to separate the front-end from the back-end.
Horizontal Scaling: Plan for horizontal scaling by ensuring that your architecture can handle high traffic by adding more web servers and balancing the load across them.

By incorporating these strategies, you’ll be better prepared to scale your Drupal site as your traffic and user base grow, without compromising performance or reliability.

1. Multisite vs. Headless: Choosing the Right Architecture for Your Needs

As you plan for scalability, it’s important to decide whether your site should be part of a multisite installation or whether a headless Drupal setup makes more sense for your specific use case. Both approaches have their own advantages and are suited to different needs.

Multisite: Efficient Management of Multiple Sites

Drupal multisite allows you to run multiple websites from a single Drupal codebase. Each site has its own database, content, configuration, and domain, but they share the same core Drupal installation, modules, and themes. This setup can be highly efficient when managing multiple sites with similar functionality, especially for organizations like universities, government agencies, or enterprises with regional websites.

When to Use Multisite:

Shared Functionality Across Sites: If you’re managing multiple sites with similar structures, features, and content, a multisite setup can save development time by sharing code and configurations across all sites.
Ease of Updates: With multisite, you only need to update the core codebase once to apply updates to all the sites, which simplifies maintenance and security updates.
Centralized Hosting: Multisite allows you to host multiple websites on a single server environment, reducing infrastructure costs.

Multisite Scalability Considerations:

Performance: Multisite can introduce performance challenges, as all sites share the same server resources. As traffic grows, you may need to invest in stronger server hardware or distributed environments.
Complexity: While multisite reduces code duplication, it can introduce complexity in managing different configurations and databases. Changes to one site can inadvertently affect others if not carefully managed.
Limitations: Multisite setups are not ideal for sites that have significantly different configurations or custom functionality. For example, if one site needs a custom module that isn’t needed by others, multisite may add unnecessary complexity.

Setting Up Multisite:

To configure multisite in Drupal, create multiple directories within the /sites folder, one for each domain or site:

/sites
  /example1.com
  /example2.com

Each directory contains its own settings.php and configuration files, but they all share the same Drupal codebase. This allows you to create a consistent development and deployment process while managing content independently across each site.

Headless Drupal: Flexibility and Decoupling

Headless Drupal (or decoupled Drupal) separates the front-end and back-end of your site. In this architecture, Drupal serves as the back-end content management system (CMS), while the front-end is built using a modern JavaScript framework like React, Vue, or Angular, which consumes Drupal’s content via APIs.

When to Use Headless Drupal:

Advanced Front-End Experiences: If you need to build highly interactive, dynamic, and fast user interfaces that go beyond what traditional Drupal theming can offer, headless Drupal allows you to use the latest front-end technologies.
Omnichannel Publishing: If your content needs to be distributed across multiple channels—such as websites, mobile apps, IoT devices, and digital signage—headless Drupal allows you to publish content once and use it everywhere via APIs.
Flexibility: Headless architecture provides greater flexibility for the front-end team to work independently from the back-end. This decoupling also allows for different front-end experiences across devices without altering Drupal’s core CMS functionality.

Headless Scalability Considerations:

Separation of Concerns: Headless Drupal scales better by offloading rendering tasks to a separate front-end layer. This reduces the load on the Drupal back-end and enables better distribution of server resources.
Caching: You can implement front-end caching layers (e.g., with Varnish or a CDN) independently of Drupal’s caching system, further improving scalability and performance for users.
API Load: If you’re delivering content via APIs, ensure your Drupal instance can handle a high volume of API requests. Use caching strategies and performance optimizations to ensure API responses are quick and scalable.

Implementing Headless Drupal:

To implement headless Drupal, you’ll need to configure Drupal to serve content via RESTful APIs, GraphQL, or JSON:API. For example, the JSON:API module provides an out-of-the-box solution to expose Drupal content as JSON, which can be consumed by a front-end application.

composer require drupal/jsonapi

After enabling JSON:API, you can access Drupal content at routes like:

/jsonapi/node/article

You can then build a front-end application using your preferred JavaScript framework that consumes this data and renders it dynamically.

2. Horizontal Scaling: Preparing for High Traffic

As your Drupal site grows, you’ll need to plan for handling increasing traffic and resource demands. One of the most effective ways to scale your Drupal site for high traffic is through horizontal scaling, which involves adding more web servers to your architecture and distributing the load across them.

What is Horizontal Scaling?

Horizontal scaling refers to adding more servers (or instances) to your architecture to distribute the load. This contrasts with vertical scaling, which involves adding more resources (CPU, memory) to a single server. Horizontal scaling offers greater flexibility and reliability, as it allows you to handle large traffic volumes by spreading requests across multiple servers.

Key Components for Horizontal Scaling in Drupal

Load Balancer: A load balancer is responsible for distributing incoming traffic across multiple web servers. By balancing the load, you ensure that no single server becomes overwhelmed, which improves performance and reliability.
Multiple Web Servers: By having multiple web servers running the same Drupal site, you can handle more concurrent users and distribute the traffic load evenly. Each server processes a portion of the requests, reducing bottlenecks.
Shared Database: In a horizontally scaled environment, all web servers must access the same database to ensure consistency. Typically, this involves hosting the database on a dedicated, scalable server, such as Amazon RDS or another database-as-a-service solution.
File Storage: For a multi-server setup, you’ll need shared file storage. Instead of storing user-uploaded files locally on each server, use a centralized storage system like Amazon S3 or NFS to ensure all servers have access to the same files.
Caching Layer: Caching plays a vital role in improving performance in high-traffic environments. Use caching mechanisms like Varnish, Redis, or Memcached to reduce the number of requests Drupal needs to process by caching content and API responses.

Horizontal Scaling in Practice

Step 1: Set Up Load Balancing

To implement horizontal scaling, you need a load balancer to distribute traffic across your web servers. Common load balancer services include:

Amazon Elastic Load Balancer (ELB): Automatically distributes incoming traffic to multiple EC2 instances.
Nginx: An open-source load balancer you can configure manually to balance traffic across your servers.
HAProxy: A popular high-performance load balancer that works well with Drupal.

Example Nginx configuration for load balancing:

http {
  upstream drupal_servers {
    server web1.example.com;
    server web2.example.com;
  }

  server {
    listen 80;
    server_name example.com;

    location / {
      proxy_pass http://drupal_servers;
    }
  }
}

Step 2: Use a Shared Database

In a horizontally scaled setup, all your web servers should connect to a single, centralized database. Hosting the database on a dedicated server, such as Amazon RDS or Google Cloud SQL, ensures that it can handle the increased load and scale independently from your web servers.

Step 3: Implement Shared File Storage

For shared file storage, use a cloud-based solution like Amazon S3, where all file uploads (such as images and documents) are stored in a central location that all web servers can access.

You can configure Drupal to use S3 for file storage by installing the S3 File System module:

composer require drupal/s3fs

After configuring the module, Drupal will store all files in your S3 bucket, ensuring that they’re accessible across all servers.

Step 4: Caching for Improved Performance

To handle high traffic efficiently, set up caching mechanisms that reduce the load on your Drupal servers. You can use Varnish for HTTP caching, Redis or Memcached for application-level caching, and CDNs like Cloudflare or Fastly to cache static assets globally.

Conclusion

As your Drupal website grows, scalability becomes a critical consideration

for ensuring that your site remains fast, reliable, and responsive to user demands. By carefully planning your architecture—whether using multisite for multiple site management or headless Drupal for flexible, decoupled front-ends—you can build a system that is easy to maintain and scale.

Additionally, incorporating horizontal scaling ensures that your site can handle large traffic volumes by distributing the load across multiple web servers. By leveraging load balancers, shared databases, centralized file storage, and caching layers, you’ll create a high-performance environment capable of supporting rapid growth.

Following these best practices will allow you to future-proof your Drupal site, ensuring it remains scalable, high-performing, and responsive to users, no matter how much traffic it attracts.

Scalability Considerations